This invention relates generally to cable laying plows and more particularly concerns a cable laying plow adapted for cutting roots and vegetable matter accumulating on and about the plow as it is used to lay cable.
Heretofore, specialized cable laying plows have been used to bury cable such as telephone cable beneath the surface of the earth. Such plows have typically been attached to and dragged behind a vehicle such as a crawler tractor. The plow itself is often a steel shank angled downward and forward and having a sharpened leading edge. A vibrating device having, for example, an unbalanced rotating shaft, may be interposed between the tractor and the shank to assist the shank in breaking the soil. The shank is followed by a cable chute connected to the trailing edge of the shank through which the cable is placed into the trench cut by the plow.
As the shank is dragged through the earth, it commonly encounters vegetable matter in the earth such as tree roots and the like. More deeply buried roots, for example those buried more than two feet deep, are generally confined by the weight of the soil overburden above them and are more easily snapped in place by the shank at the point of contact of the root with the shank. Typically, all portions of a root that is snapped in this manner remain in the earth and do not foul the plow.
Roots nearer to the surface of the earth, for example in the uppermost twelve inches, are more likely to foul the shank. Movement of these surface roots is less restricted by the smaller confining weight of overburden. Additionally, in some soils, the surface soils are less confining, being less consolidated than deeper soils or containing more organic matter. The reduced tendency of the surface soils to confine roots causes the plow to push a root rather than to snap it. As the root is pushed, it may be stretched and eventually may break under tension at a point other than the point of contact with the shank, leaving a segment of the root wrapped about the shank.
As the shank is dragged through the earth, other root segments accumulate about the shank, particularly about its upper end. If an angled plow shank is used, forward motion of the plow urges deeper root segments to the upper end of the shank. As these roots accumulate, their mass effectively increases the width of the shank, thereby increasing both the width of the trench and the effort required to cover the trench after the cable is laid. The resistance of the earth to the forward motion of the plow compacts the root segments tightly about the shank. Eventually, the root mass must be removed from the shank such as by laborers with axes, which manual removal can require as long as thirty minutes.
Vegetation cutting or cleaning plows have been suggested in attempts to address this problem. U.S. Pat. No. 3,777,500 to Kelley discloses vegetation cutting structure for cutting both the earth and vegetation lying in the path of the plow. Kelley's plow has continuously reciprocating saw teeth along the entire leading edge of its shank to "saw" through the earth and through any vegetation therein such as grasses. U.S. Pat. No. 3,831,299 to Kelley discloses a cable laying plow that resembles a chain saw.
U.S. Pat. No. 3,706,207 to Cornelius discloses in one embodiment continuously reciprocating saw teeth along the leading edge of the shank. In another embodiment, Cornelius discloses a straight leading edge shank above a reciprocating projecting tip. The gap between the lower flat edge of the shank and the upper flat surface of the tip expands and contacts as the tip reciprocates. However, it appears that root material entering this gap may lodge behind and under the reciprocating tip, eventually encumbering its reciprocation.
U.S. Pat. No. 4,200,410 to Baker discloses a fixed knife edge at the surface of the earth to cut roots, and, in a separate embodiment, fixed saw teeth.
Accordingly, it is an object of this invention to provide an improved root cutting cable laying plow.
It is a further object of this invention to provide a root cutting cable laying plow capable of cutting accumulated roots and vegetable matter from the plow.